Calmodulin-dependent phosphatase, kinases, and transcriptional corepressors involved in T-cell activation

Cyclophilin A: promising target in cancer therapy

Cyclophilin A (CypA), a member of the immunophilin family, stands out as the most prevalent among the cyclophilins found in humans. Beyond serving as the intracellular receptor for the immunosuppressive drug cyclosporine A (CsA), CypA exerts critical functions within the cell via its peptidyl-prolyl cis-trans isomerase (PPIase) activity, which is crucial for processes, such as protein folding, trafficking, assembly, modulation of immune responses, and cell signaling. Increasing evidence indicates that CypA is up-regulated in a variety of human cancers and it may be a novel potential therapeutic target for cancer treatment. Therefore, gaining a thorough understanding of CypA's contribution to cancer could yield fresh perspectives and inform the development of innovative therapeutic approaches. This review delves into the multifaceted roles of CypA in cancer biology and explores the therapeutic potential of targeting CypA.

Leishmania exploits host cAMP/EPAC/calcineurin signaling to induce an IL-33-mediated anti-inflammatory environment for the establishment of infection

Host anti-inflammatory responses are critical for the progression of visceral leishmaniasis, and the pleiotropic cytokine interleukin (IL)-33 was found to be upregulated in infection. Here, we documented that IL-33 induction is a consequence of elevated cAMP-mediated exchange protein activated by cAMP (EPAC)/calcineurin-dependent signaling and essential for the sustenance of infection. Leishmania donovani-infected macrophages showed upregulation of IL-33 and its neutralization resulted in decreased parasite survival and increased inflammatory responses. Infection-induced cAMP was involved in IL-33 production and of its downstream effectors PKA and EPAC, only the latter was responsible for elevated IL-33 level. EPAC initiated Rap-dependent phospholipase C activation, which triggered the release of intracellular calcium followed by calcium/calmodulin complex formation. Screening of calmodulin-dependent enzymes affirmed involvement of the phosphatase calcineurin in cAMP/EPAC/calcium/calmodulin signaling-induced IL-33 production and parasite survival. Activated calcineurin ensured nuclear localization of the transcription factors, nuclear factor of activated T cell 1 and hypoxia-inducible factor 1 alpha required for IL-33 transcription, and we further confirmed this by chromatin immunoprecipitation assay. Administering specific inhibitors of nuclear factor of activated T cell 1 and hypoxia-inducible factor 1 alpha in BALB/c mouse model of visceral leishmaniasis decreased liver and spleen parasite burden along with reduction in IL-33 level. Splenocyte supernatants of inhibitor-treated infected mice further documented an increase in tumor necrosis factor alpha and IL-12 level with simultaneous decrease of IL-10, thereby indicating an overall disease-escalating effect of IL-33. Thus, this study demonstrates that cAMP/EPAC/calcineurin signaling is crucial for the activation of IL-33 and in effect creates anti-inflammatory responses, essential for infection.

Understanding the pathogenic significance of altered calcium-calmodulin signaling in T cells in autoimmune diseases

Calcium/calmodulin-dependent protein kinase IV (CaMK4) serves as a pivotal mediator in the regulation of gene expression, influencing the activity of transcription factors within a variety of immune cells, including T cells. Altered CaMK4 signaling is implicated in autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, and psoriasis, which are characterized by dysregulated immune responses and clinical complexity. These conditions share common disturbances in immune cell functionality, cytokine production, and autoantibody generation, all of which are associated with disrupted calcium-calmodulin signaling. This review underscores the consequences of dysregulated CaMK4 signaling across these diseases, with an emphasis on its impact on Th17 differentiation and T cell metabolism-processes central to maintaining immune homeostasis. A comprehensive understanding of roles of CaMK4 in gene regulation across various autoimmune disorders holds promise for the development of targeted therapies, particularly for diseases driven by Th17 cell dysregulation.

Back on the scene: advances and challenges in CD3-related drugs in tumor therapy

CD3 molecules are mainly distributed on the membrane of mature T cells. They are involved in T cell antigen recognition, signal transduction, and regulation of T cell development. CD3-related monoclonal antibodies (mAbs) are mainly used in the treatment of autoimmune diseases. Nearly half of all bispecific antibodies developed are used in tumor therapy, one of which is CD3 antigen. In this review, we discuss the importance of biological function and the crucial role of CD3 in tumor therapy. We highlight the research status of antibodies and small molecules targeting CD3 to provide guidance for future drug research.

The Genetic Landscape of Ocular Adnexa MALT Lymphoma Reveals Frequent Aberrations in NFAT and MEF2B Signaling Pathways

A comprehensive constellation of somatic non-silent mutations and copy number (CN) variations in ocular adnexa marginal zone lymphoma (OAMZL) is unknown. By utilizing whole-exome sequencing in 69 tumors we define the genetic landscape of OAMZL. Mutations and CN changes in CABIN1 (30%), RHOA (26%), TBL1XR1 (22%), and CREBBP (17%) and inactivation of TNFAIP3 (26%) were among the most common aberrations. Candidate cancer driver genes cluster in the B-cell receptor (BCR), NFkB, NOTCH and NFAT signaling pathways. One of the most commonly altered genes is CABIN1, a calcineurin inhibitor acting as a negative regulator of the NFAT and MEF2B transcriptional activity. CABIN1 deletions enhance BCR-stimulated NFAT and MEF2B transcriptional activity, while CABIN1 mutations enhance only MEF2B transcriptional activity by impairing binding of mSin3a to CABIN1. Our data provide an unbiased identification of genetically altered genes that may play a role in the molecular pathogenesis of OAMZL and serve as therapeutic targets.

A comprehensive review on possibilities of treating psoriasis using dermal cyclosporine

Psoriasis is an autoimmune, chronic proliferative, inflammatory skin disease with high comorbidity. Psoriasis is not a curable disease; it can only be managed. Cyclosporine A (CyA) is one of the FDA-approved immunosuppressant drug used in severe Psoriasis. Till date only oral route is used for its administration. Administration of CyA by this route causes serious side effects such as hypertension and renal toxicity. Due to these side effects, a number of researches have been done and taking place in the current times for the dermal delivery of CyA for the management of psoriasis. Dermal delivery of CyA is not an easy task because of its physiochemical properties like high molecular weight, lipophilicity and resistance offered by stratum corneum (SC). Because of the above problems in the dermal delivery a number of new approaches such as nanolipid carriers, microemulsion, liposomes, niosomes etc. are explored. To those deep findings for psoriasis management with dermal delivery of CyA have not been discussed. This comprehensive review includes all the studies, advancements and their critical findings which took place in the recent times for the dermal delivery of CyA and along with the suitable modification needed for the efficient dermal delivery of CyA are also suggested.

Peroxisome Proliferator-Activated Receptor-Gamma (PPAR-ɣ): Molecular Effects and Its Importance as a Novel Therapeutic Target for Cerebral Ischemic Injury

Cerebral ischemic injury is a leading cause of death and long-term disability throughout the world. Peroxisome proliferator-activated receptor gamma (PPAR-ɣ) is a ligand-activated nuclear transcription factor that is a member of the PPAR family. PPAR-ɣ has been shown in several in vitro and in vivo models to prevent post-ischemic inflammation and neuronal damage by negatively controlling the expression of genes modulated by cerebral ischemic injury, indicating a neuroprotective effect during cerebral ischemic injury. A extensive literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out to understand the nature of the extensive work done on the mechanistic role of Peroxisome proliferator activated receptor gamma and its modulation in Cerebral ischemic injury. PPAR-ɣ can interact with specific DNA response elements to control gene transcription and expression when triggered by its ligand. It regulates lipid metabolism, improves insulin sensitivity, modulates antitumor mechanisms, reduces oxidative stress, and inhibits inflammation. This review article provides insights on the current state of research into the neuroprotective effects of PPAR-ɣ in cerebral ischemic injury, as well as the cellular and molecular mechanisms by which these effects are modulated, such as inhibition of inflammation, reduction of oxidative stress, suppression of pro-apoptotic production, modulation of transcription factors, and restoration of injured tissue through neurogenesis and angiogenesis.

Cannabinoid-induced changes in the immune system: The role of microRNAs

Naturally occurring cannabinoids have been used by humans for their medicinal benefits for over several millennia. While the use of cannabinoids has been strictly regulated in the past century, easing of state regulations has been associated with an increase in use of cannabinoids in the United States. The potential therapeutic applications of cannabinoids have been explored and the anti-inflammatory effect of cannabis-derived cannabinoids has been well-documented. The pharmacological effects of cannabinoids are governed by the modulation of cannabinoid receptors, CB₁ and CB₂, expressed in the central and peripheral tissues. Moreover, growing scientific evidence suggests that the cannabinoid-mediated changes in the immune system involves change in expression of microRNAs (miRNAs). MiRNAs are short non-coding, single-stranded RNA which have the ability to affect post-translational regulation of gene expression. Studies over the past decade have investigated the changes in expression of miRNAs following treatment of various components of the immune system with different chemical modulators of the cannabinoid receptors. Such studies have highlighted the key role played by various miRNAs in driving the observed immunomodulatory effects of cannabinoids. The aim of this review article, therefore, is to summarize the role of miRNAs behind the observed effects of cannabinoids on the overall immune system, rather than focusing on a single disease state.

Modulatory function of calmodulin on phagocytosis and potential regulation mechanisms in the blood clam Tegillarca granosa

Unlike vertebrate species, invertebrates lack antigen-antibody mediated immune response and mainly rely on haemocyte phagocytosis to fight against pathogen infection. Recently, studies conducted in model vertebrates demonstrated that the multifunctional protein calmodulin (CaM) plays an important role in regulating immune responses. However, the intrinsic relation between CaM and phagocytosis process remains poorly understood in invertebrate species such as bivalve mollusks. Therefore, in the present study, the immunomodulatory function of CaM on haemocyte phagocytosis was verified in the blood clam, Tegillarca granosa, using the CaM-specific inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7). Results obtained show that CaM inhibition significantly suppressed the phagocytic activity of haemocytes. In addition, CaM inhibition constrained intracellular Ca²⁺ elevation, hampered actin cytoskeleton assembly, suppressed calcineurin (CaN) activity, and disrupted NF-κB activation in haemocytes upon LPS induction. Furthermore, expression of seven selected genes from the actin cytoskeleton regulation- and immune-related pathways were significantly downregulated whereas those of CaM and CaN from the Ca²⁺-signaling pathway were significantly upregulated by in vitro incubation of haemocytes with W-7. For the first time, the present study demonstrated that CaM play an important role in phagocytosis modulation in bivalve species. In addition, the intracellular Ca²⁺ and downstream Ca²⁺-signaling-, actin cytoskeleton regulation-, and immune-related pathways offer candidate routes through which CaM modulates phagocytosis.

'Nur'turing tumor T cell tolerance and exhaustion: novel function for Nuclear Receptor Nur77 in immunity

The nuclear receptor Nur77 is expressed in a multitude of tissues, regulating cell differentiation and homeostasis. Dysregulation of Nur77 signaling is associated with cancer, cardiovascular disease, and disorders of the CNS. The role of Nur77 in T cells has been studied for almost 30 years now. There is a clear appreciation that Nur77 is crucial for apoptosis of self‐reactive T cells. However, the regulation and function of Nur77 in mature T cells remains largely unclear. In an exciting development, Nur77 has been recently demonstrated to impinge on cancer immunotherapy involving chimeric antigen receptor (CAR) T cells and tumor infiltrating lymphocytes (TILs). These studies indicated that Nur77 deficiency reduced T cell tolerance and exhaustion, thus raising the effectiveness of immune therapy in mice. Based on these novel insights, it may be proposed that regulation of Nur77 activity holds promise for innovative drug development in the field of cellular immunotherapy in cancer. In this review, we therefore summarize the role of Nur77 in T cell selection and maturation; and further develop the idea of targeting its activity in these cells as a potential strategy to augment current cancer immunotherapy treatments.

SAR study of bisamides as cyclophilin a inhibitors for the development of host-targeting therapy for hepatitis C virus infection

The therapy of chronic hepatitis C virus infections has significantly improved with the development of direct-acting antivirals (DAAs), which contain NS3/4A protease, NS5A, and NS5B polymerase inhibitors. However, mutations in specific residues in these viral target genes are associated with resistance to the DAAs. Especially inhibitors of NS3/4A protease and NS5A, such as grazoprevir and velpatasvir, have a low barrier to resistant mutations. As a result, the mutations influence the virological outcomes after DAA treatment. CypA inhibitors, as host-targeted agents, act on host factors to inhibit HCV replication, exhibiting a high resistance barrier and pan-genotype activities against HCV. Therefore, they can be developed into alternative, more effective anti-HCV agents. However, CypA inhibitors are natural products and analogs. Based on previous studies, bisamide derivatives were designed and synthesized to develop a novel class of CypA inhibitors. Bisamide derivative 7c is a promising compound with potent anti-HCV activity at subtoxic concentrations. Surface plasmon resonance experiments revealed that 7c directly binds to CypA. All these studies indicated that the derivative 7c is a potent CypA inhibitor, which can be used as a host-targeted agent in combination with other antiviral agents for anti-HCV treatment.

GSK3 inhibition with low dose lithium supplementation augments murine muscle fatigue resistance and specific force production

Calcineurin is a Ca2+ -dependent serine/threonine phosphatase that dephosphorylates nuclear factor of activated T cells (NFAT), allowing for NFAT entry into the nucleus. In skeletal muscle, calcineurin signaling and NFAT activation increases the expression of proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α) and slow myosin heavy chain (MHC) I ultimately promoting fatigue resistance. Glycogen synthase kinase 3 (GSK3) is a serine/threonine kinase that antagonizes calcineurin by re-phosphorylating NFAT preventing its entry into the nucleus. Here, we tested whether GSK3 inhibition in vivo with low dose lithium chloride (LiCl) supplementation (10 mg kg-1  day-1 for 6 weeks) in male C57BL/6J mice would enhance muscle fatigue resistance in soleus and extensor digitorum longus (EDL) muscles by activating NFAT and augmenting PGC-1α and MHC I expression. LiCl treatment inhibited GSK3 by elevating Ser9 phosphorylation in soleus (+1.8-fold, p = .007) and EDL (+1.3-fold p = .04) muscles. This was associated with a significant reduction in NFAT phosphorylation (-50%, p = .04) and a significant increase in PGC-1α (+1.5-fold, p = .05) in the soleus but not the EDL. MHC isoform analyses in the soleus also revealed a 1.2-fold increase in MHC I (p = .04) with no change in MHC IIa. In turn, a significant enhancement in soleus muscle fatigue (p = .04), but not EDL (p = .26) was found with LiCl supplementation. Lastly, LiCl enhanced specific force production in both soleus (p < .0001) and EDL (p = .002) muscles. Altogether, our findings show the skleletal muscle contractile benefits of LiCl-mediated GSK3 inhibition in mice.

Ca2+ functions as a molecular switch that controls the mutually exclusive complex formation of pyridoxal phosphatase with CIB1 or calmodulin

Pyridoxal 5'-phosphate (PLP) is an essential cofactor for neurotransmitter metabolism. Pyridoxal phosphatase (PDXP) deficiency in mice increases PLP and γ-aminobutyric acid levels in the brain, yet how PDXP is regulated is unclear. Here, we identify the Ca2+ - and integrin-binding protein 1 (CIB1) as a PDXP interactor by yeast two-hybrid screening and find a calmodulin (CaM)-binding motif that overlaps with the PDXP-CIB1 interaction site. Pulldown and crosslinking assays with purified proteins demonstrate that PDXP directly binds to CIB1 or CaM. CIB1 or CaM does not alter PDXP phosphatase activity. However, elevated Ca2+ concentrations promote CaM binding and, thereby, diminish CIB1 binding to PDXP, as both interactors bind in a mutually exclusive way. Hence, the PDXP-CIB1 complex may functionally differ from the PDXP-Ca2+ -CaM complex.

A Compartmentalized Reduction in Membrane-Proximal Calmodulin Reduces the Immune Surveillance Capabilities of CD8+ T Cells in Head and Neck Cancer

The limited ability of cytotoxic CD8+ T cells to infiltrate solid tumors and function within the tumor microenvironment presents a major roadblock to effective immunotherapy. Ion channels and Ca2+-dependent signaling events control the activity of T cells and are implicated in the failure of immune surveillance in cancer. Reduced KCa3.1 channel activity mediates the heightened inhibitory effect of adenosine on the chemotaxis of circulating T cells from head and neck squamous cell carcinoma (HNSCC) patients. Herein, we conducted experiments that elucidate the mechanisms of KCa3.1 dysfunction and impaired chemotaxis in HNSCC CD8+ T cells. The Ca2+ sensor calmodulin (CaM) controls multiple cellular functions including KCa3.1 activation. Our data showed that CaM expression is lower in HNSCC than healthy donor (HD) T cells. This reduction was due to an intrinsic decrease in the genes encoding CaM combined to the failure of HNSCC T cells to upregulate CaM upon activation. Furthermore, the reduction in CaM was confined to the plasma membrane and resulted in decreased CaM-KCa3.1 association and KCa3.1 activity (which was rescued by the delivery of CaM). IFNγ production, also Ca2+- and CaM-dependent, was instead not reduced in HNSCC T cells, which maintained intact cytoplasmic CaM and Ca2+ fluxing ability. Knockdown of CaM in HD T cells decreased KCa3.1 activity, but not IFNγ production, and reduced their chemotaxis in the presence of adenosine, thus recapitulating HNSCC T cell dysfunction. Activation of KCa3.1 with 1-EBIO restored the ability of CaM knockdown HD T cells to chemotax in the presence of adenosine. Additionally, 1-EBIO enhanced INFγ production. Our data showed a localized downregulation of membrane-proximal CaM that suppressed KCa3.1 activity in HNSCC circulating T cells and limited their ability to infiltrate adenosine-rich tumor-like microenvironments. Furthermore, they indicate that KCa3.1 activators could be used as positive CD8+ T cell modulators in cancers.

Molecular design, synthesis, and biological evaluation of bisamide derivatives as cyclophilin A inhibitors for HCV treatment

Hepatitis C virus (HCV) is a major cause of end-stage liver diseases. Direct-acting antivirals (DAAs), including inhibitors of nonstructural proteins (NS3/4A protease, NS5A, and NS5B polymerase), represent key components of anti-HCV treatment. However, some DAAs are associated with increased drug resistance and undesired side effects. Previous reports have shown that bisamides could be a novel class of cyclophilin A (CypA) inhibitors for treating HCV as a member of combinational therapies. To fully elucidate structure-activity relationships of bisamide derivatives and find a better hit compound with diverse binding modes, 16 biamides were designed with the help of docking program. They were then synthesized using one-pot four-component Ugi reaction. 7e with selectivity index of more than 18.9 (50% effective concentration of 5.3 μM, but no cytotoxicity at 100 μM) and unique binding mode that could be dived into gatekeeper pocket was selected as a new hit compound. Surface plasmon resonance experiments revealed that 7e is able to bind to CypA with a K_D of 3.66 μM. Taken together, these results suggest that 7e as a CypA inhibitor could be used as an alternative anti-HCV agent in combinational therapy in the future.

Pulmonary Colonization Resistance to Pathogens via Noncanonical Wnt and Interleukin-17A by Intranasal pep27 Mutant Immunization

Background

Previous studies have focused on colonization resistance of the gut microbiota against antibiotic resistant strains. However, less research has been performed on respiratory colonization resistance.

Methods

Because respiratory colonization is the first step of respiratory infections, intervention to prevent colonization would represent a new approach for preventive and therapeutic measures. The Th17 response plays an important role in clearance of respiratory pathogens. Thus, harnessing the Th17 immune response in the mucosal site would be an effective method to design a respiratory mucosal vaccine.

Results

In this study, we show that intranasal Δpep27 immunization induces noncanonical Wnt and subsequent interleukin (IL)-17 secretion, and it inhibits Streptococcus pneumoniae, Staphylococcus aureus, and Klebsiella pneumoniae colonization. Moreover, IL-17A neutralization or nuclear factor of activated T-cell inhibition augmented bacterial colonization, indicating that noncanonical Wnt signaling is involved in pulmonary colonization resistance.

Conclusions

Therefore, Δpep27 immunization can provide nonspecific respiratory colonization resistance via noncanonical Wnt signaling and IL-17A-related pathways.

Tacrolimus treatment for infertility related to maternal-fetal immune interactions

Many approaches have been used to achieve successful pregnancies in patients with infertility, though existing treatments remain unsatisfactory in patients with infertility caused by abnormal maternal-fetal immunity. However, our understanding of the immunological aspects of infertility has steadily progressed, aided by recent research into organ transplantation and cancer. The results of these recent analyses have led to the development and evaluation of several candidate immunological treatments, but the use of immunological treatments remains a novel approach. The current paper presents the hypothesis that tacrolimus may have potential as a candidate agent for the treatment of maternal-fetal immunity-related infertility.

Rapamycin-inspired macrocycles with new target specificity

Rapamycin and FK506 are macrocyclic natural products with an extraordinary mode of action—they form binary complexes with FKBP through a shared FKBP-binding domain before forming ternary complexes with their respective targets, mTOR and calcineurin, respectively. Inspired by this, we sought to build a rapamycin-like macromolecule library to target new cellular proteins by replacing the effector domain of rapamycin with a combinatorial library of oligopeptides. We developed a robust macrocyclization method using ring-closing metathesis and synthesized a 45,000-compound library of hybrid macrocycles that are named rapafucins using optimized FKBP-binding domains. Screening of the rapafucin library in human cells led to the discovery of rapadocin, an inhibitor of nucleoside uptake. Rapadocin is a potent, isoform-specific and FKBP-dependent inhibitor of the equilibrative nucleoside transporter 1 and is efficacious in an animal model of kidney ischemia reperfusion injury. Together, these results demonstrate that rapafucins are a new class of chemical probes and drug leads that can expand the repertoire of protein targets well beyond mTOR and calcineurin.

The TRPC6 intronic polymorphism, associated with the risk of neurological disorders in systemic lupus erythematous, influences immune cell function

Patients with systemic lupus erythematosus (SLE) carrying a TT genotype for the rs7925662 single nucleotide polymorphism (SNP) in the transient receptor potential canonical channel 6 (TRPC6) gene are more likely to develop neuropsychiatric manifestations (NPSLE). We functionally characterised the effects of TRPC6 on peripheral blood mononuclear cells from 18 patients with SLE and 8 healthy controls with a known genotype. TRPC6 influenced calcium currents, apoptosis rates and cytokine secretion in a disease- and genotype-dependent manner. Cells from TT patients with NPSLE were more dependent on TRPC6 for the generation of calcium currents.

NKILA lncRNA promotes tumor immune evasion by sensitizing T cells to activation-induced cell death

Activation-induced cell death (AICD) of T lymphocytes can be exploited by cancers to escape immunological destruction. We demonstrated that tumor-specific cytotoxic T lymphocytes (CTLs) and type 1 helper T (T_H1) cells, rather than type 2 helper T cells and regulatory T cells, were sensitive to AICD in breast and lung cancer microenvironments. NKILA, an NF-κB-interacting long noncoding RNA (lncRNA), regulates T cell sensitivity to AICD by inhibiting NF-κB activity. Mechanistically, calcium influx in stimulated T cells via T cell-receptor signaling activates calmodulin, thereby removing deacetylase from the NKILA promoter and enhancing STAT1-mediated transcription. Administering CTLs with NKILA knockdown effectively inhibited growth of breast cancer patient-derived xenografts in mice by increasing CTL infiltration. Clinically, NKILA overexpression in tumor-specific CTLs and T_H1 cells correlated with their apoptosis and shorter patient survival. Our findings underscore the importance of lncRNAs in determining tumor-mediated T cell AICD and suggest that engineering lncRNAs in adoptively transferred T cells might provide a novel antitumor immunotherapy.

Ginsenosides from Korean red ginseng modulate T cell function via the regulation of NF-AT-mediated IL-2 production

Korean red ginseng is a traditional health food frequently used to prevent or treat various diseases worldwide. In this study, we evaluated the immunomodulatory activities of eleven compounds (1-11) isolated from Korean red ginseng, focusing on T cell function. First, the effects of the eleven compounds were studied on the regulation of IL-2, a potent T cell growth factor. Compounds 5, 7, and 9 significantly increased IL-2 secretion in phorbol 12-myristate 13-acetate (PMA)/ionomycin (Io)-induced EL-4 T cells. Next, we examined the effects of compounds 5, 7, and 9 on the regulation of transcription factors related to IL-2 production in T cells. Compound 9 significantly increased the PMA/Io-induced promoter activity of nuclear factor of activated T cells (NF-AT) in EL-4 T cells, but did not have any significant effects on the promoters of NF- κB. These results suggest that compound 9 activates T cell function via the regulation of NF-AT-mediated IL-2 production.

Calcineurin-mediated IL-2 production by CD11chighMHCII+ myeloid cells is crucial for intestinal immune homeostasis

The intestinal immune system can respond to invading pathogens yet maintain immune tolerance to self-antigens and microbiota. Myeloid cells are central to these processes, but the signaling pathways that underlie tolerance versus inflammation are unclear. Here we show that mice lacking Calcineurin B in CD11c^highMHCII⁺ cells (Cnb1^CD11c mice) spontaneously develop intestinal inflammation and are susceptible to induced colitis. In these mice, colitis is associated with expansion of T helper type 1 (Th1) and Th17 cell populations and a decrease in the number of FoxP3⁺ regulatory T (Treg) cells, and the pathology is linked to the inability of intestinal Cnb1-deficient CD11c^highMHCII⁺ cells to express IL-2. Deleting IL-2 in CD11c^highMHCII⁺ cells induces spontaneous colitis resembling human inflammatory bowel disease. Our findings identify that the calcineurin–NFAT–IL-2 pathway in myeloid cells is a critical regulator of intestinal homeostasis by influencing the balance of inflammatory and regulatory responses in the mouse intestine.

Treg cells can maintain intestinal homeostasis and limit intestinal bowel disease. Here the authors use a mouse model of spontaneous colitis to show that calcineurin-NFAT-induced IL-2 production by dendritic cells regulates the balance between Treg and effector T cells in the gut lamina propria.

Regulation of T-Cell Signaling by Post-Translational Modifications in Autoimmune Disease

The adaptive immune system involves antigen-specific host defense mechanisms mediated by T and B cells. In particular, CD4⁺ T cells play a central role in the elimination of pathogens. Immunological tolerance in the thymus regulates T lymphocytes to avoid self-components, including induction of cell death in immature T cells expressing the self-reactive T-cell receptor repertoire. In the periphery, mature T cells are also regulated by tolerance, e.g., via induction of anergy or regulatory T cells. Thus, T cells strictly control intrinsic signal transduction to prevent excessive responses or self-reactions. If the inhibitory effects of T cells on these mechanisms are disrupted, T cells may incorrectly attack self-components, which can lead to autoimmune disease. The functions of T cells are supported by post-translational modifications, particularly phosphorylation, of signaling molecules, the proper regulation of which is controlled by endogenous mechanisms within the T cells themselves. In recent years, molecular targeted agents against kinases have been developed for treatment of autoimmune diseases. In this review, we discuss T-cell signal transduction in autoimmune disease and provide an overview of acetylation-mediated regulation of T-cell signaling pathways.

The role of CaMK4 in immune responses

Calcium/calmodulin-dependent protein kinase IV (CaMK4) is a multifunctional serine/threonine kinase that regulates gene expression by activating transcription factors in a wide range of immune cells including T cells and antigen-presenting cells. The function of CaMK4 is suggested to be abnormal mainly in systemic lupus erythematosus (SLE), which is characterized by autoantibody production, immune complex formation, and immune dysregulation. Although accumulating evidence indicates that CaMK4 plays important roles in the immune responses, the precise molecular mechanisms underlying the development of autoimmune diseases and inflammatory disorders have not been established. In this review, we briefly summarize the role of CaMK4 in immune responses. We also discuss T-cell signaling pathways that control interleukin (IL)-17 production in patients with lupus nephritis and in glomerulonephritis in lupus-prone mice. A better understanding of the signaling and gene regulation of CaMK4 will lead to the identification of novel therapeutic targets in Th17 driven-autoimmune diseases.

Estrogen receptor α/HDAC/NFAT axis for delphinidin effects on proliferation and differentiation of T lymphocytes from patients with cardiovascular risks

Delphinidin, an anthocyanin present in red wine, has been reported to preserve the integrity of endothelium via an estrogen receptor alpha (ERα)-dependent mechanism. However, the effect of delphinidin on the immune response in obesity-related inflammation remains unknown. Given the important role of T lymphocytes in obesity-related inflammation, we investigated the effect of delphinidin on proliferation and differentiation of T lymphocytes from healthy subjects and metabolic syndrome patients. Delphinidin decreased the proliferation stimulated by different agents acting through different mechanisms. This effect of delphinidin was associated with its ability to inhibit Ca²⁺ signaling via reduced store-operated Ca²⁺ entry and release, and subsequent decrease of HDAC and NFAT activations. Delphinidin also inhibited ERK1/2 activation. Pharmacological inhibition of ER with fulvestrant, or deletion of ERα, prevented the effect of delphinidin. Further, delphinidin suppressed the differentiation of T cells toward Th1, Th17 and Treg without affecting Th2 subsets. Interestingly, delphinidin inhibited both proliferation and differentiation of T cells taken from patients with cardiovascular risks associated with metabolic syndrome. Together, we propose that delphinidin, by acting on ERα via multiple cellular targets, may represent a new approach against chronic inflammation associated with T lymphocyte activation, proliferation and differentiation, in patients with cardiovascular risk factors.

Systems Biology Reveals NS4B-Cyclophilin A Interaction: A New Target to Inhibit YFV Replication

Yellow fever virus (YFV) replication is highly dependent on host cell factors. YFV NS4B is reported to be involved in viral replication and immune evasion. Here interactions between NS4B and human proteins were determined using a GST pull-down assay and analyzed using 1-DE and LC-MS/MS. We present a total of 207 proteins confirmed using Scaffold 3 Software. Cyclophilin A (CypA), a protein that has been shown to be necessary for the positive regulation of flavivirus replication, was identified as a possible NS4B partner. 59 proteins were found to be significantly increased when compared with a negative control, and CypA exhibited the greatest difference, with a 22-fold change. Fisher's exact test was significant for 58 proteins, and the p value of CypA was the most significant (0.000000019). The Ingenuity Systems software identified 16 pathways, and this analysis indicated sirolimus, an mTOR pathway inhibitor, as a potential inhibitor of CypA. Immunofluorescence and viral plaque assays showed a significant reduction in YFV replication using sirolimus and cyclosporine A (CsA) as inhibitors. Furthermore, YFV replication was strongly inhibited in cells treated with both inhibitors using reporter BHK-21-rep-YFV17D-LucNeoIres cells. Taken together, these data suggest that CypA-NS4B interaction regulates YFV replication. Finally, we present the first evidence that YFV inhibition may depend on NS4B-CypA interaction.

Autumnalamide targeted proteins of the immunophilin family

Previous works with autumnalamide reported that Store Operated Calcium (SOC) channels were blocked through mitochondrial modulation. In the present paper we studied the effect of autumnalamide on ionomycin Ca²⁺ fluxes. Thus, autumnalamide did not modify ionomycin-sensitive intracellular pools while the ionomycin-induced Ca²⁺ influx was blocked with similar potency whether the incubation was done before or after ionomycin-sensitive pools depletion. Nevertheless, autumnalamide was not able to inhibit ionomycin-induced Ca²⁺ influx once the membrane channels were activated. Moreover, the compound efficiently inhibited flufenamic acid (FFA) Ca²⁺ release induced in this organelle but no the next influx. Since in previous work the effect of autumnalamide was inhibited by cyclosporine A (CsA), structures that target this drug were studied. Therefore, the affinity of autumnalamide for cyclophilin D (Cyp D) was examined. The K_D obtained for Cyp D- autumnalamide was 1.51±1.399. Moreover, the K_D for Cyp A- autumnalamide was calculated. The peptide had a similar order of Cyp A binding affinity than CsA (8.08±1.23 and 6.85±1.1μM respectively). After testing autumnalamide-binding capacity for Cyp A, the activity of this compound on Cyp A pathway was tested. Thus, the effect on interleukin (IL)-2 release on activated T-lymphocytes was checked. Autumnalamide was able to reduce IL-2 levels near to T cells in resting conditions. Next, the effect over calcineurin and NFATc1 was also evaluated. While CsA inhibits both calcineurin and NFATc1, autumnalamide did not produce any effect. From these results we can conclude that, autumnalamide targeted mitochondrion and prevent T-cells from IL-2 production through the modulation of SOC Ca²⁺ channels.

New challenges and promises in solid organ transplantation pharmacogenetics: the genetic variability of proteins involved in the pharmacodynamics of immunosuppressive drugs

Interindividual variability in immunosuppressive drug responses might be partly explained by genetic variants in proteins involved in the immune response or associated with IS pharmacodynamics. On a general basis, the pharmacogenetics of drug target proteins is less known and understood than that of proteins involved in drug disposition pathways. The aim of this review is to facilitate research related to the pharmacodynamics of the main immunosuppressive drugs used in solid organ transplantation. We elaborated a quality of evidence grading system based on a literature review and identified 'highly recommended', 'recommended' or 'potential' candidates for further research. It is likely that a number of additional rare variants might further explain drug response phenotypes in transplantation, and particularly the most severe ones. The advent of next-generation sequencing will help to identify those variants.

Evaluation of Intracellular Signaling Downstream Chimeric Antigen Receptors

CD19-targeting CAR T cells have shown potency in clinical trials targeting B cell leukemia. Although mainly second generation (2G) CARs carrying CD28 or 4-1BB have been investigated in patients, preclinical studies suggest that third generation (3G) CARs with both CD28 and 4-1BB have enhanced capacity. However, little is known about the intracellular signaling pathways downstream of CARs. In the present work, we have analyzed the signaling capacity post antigen stimulation in both 2G and 3G CARs. 3G CAR T cells expanded better than 2G CAR T cells upon repeated stimulation with IL-2 and autologous B cells. An antigen-driven accumulation of CAR+ cells was evident post antigen stimulation. The cytotoxicity of both 2G and 3G CAR T cells was maintained by repeated stimulation. The phosphorylation status of intracellular signaling proteins post antigen stimulation showed that 3G CAR T cells had a higher activation status than 2G. Several proteins involved in signaling downstream the TCR were activated, as were proteins involved in the cell cycle, cell adhesion and exocytosis. In conclusion, 3G CAR T cells had a higher degree of intracellular signaling activity than 2G CARs which may explain the increased proliferative capacity seen in 3G CAR T cells. The study also indicates that there may be other signaling pathways to consider when designing or evaluating new generations of CARs.

Structure-Based Discovery of Novel Cyclophilin A Inhibitors for the Treatment of Hepatitis C Virus Infections

Hepatitis C virus (HCV) is a major cause of end-stage liver disease. Direct-acting antivirals (DAAs), including inhibitors of nonstructural proteins (NS3/4A protease, NS5A, and NS5B polymerase), represent key components of anti-HCV treatment, but these are associated with increased drug resistance and toxicity. Thus, the development of host-targeted antiviral agents, such as cyclophilin A inhibitors, is an alternative approach for more effective, selective, and safer treatment. Starting with the discovery of a bis-amide derivative 5 through virtual screening, the lead compound 25 was developed using molecular modeling-based design and systematic exploration of the structure-activity relationship. The lead 25 lacked cytotoxicity, had potent anti-HCV activity, and showed selective and high binding affinity for CypA. Unlike cyclosporin A, 25 lacked immunosuppressive effects, successfully inhibited the HCV replication, restored host immune responses without acute toxicity in vitro and in vivo, and exhibited a high synergistic effect in combination with other drugs. These findings suggest that the bis-amides have significant potential to extend the arsenal of HCV therapeutics.

Induced miR-99a expression represses Mtor cooperatively with miR-150 to promote regulatory T-cell differentiation

Peripheral induction of regulatory T (Treg) cells provides essential protection from inappropriate immune responses. CD4(+) T cells that lack endogenous miRNAs are impaired to differentiate into Treg cells, but the relevant miRNAs are unknown. We performed an overexpression screen with T-cell-expressed miRNAs in naive mouse CD4(+) T cells undergoing Treg differentiation. Among 130 candidates, the screen identified 29 miRNAs with a negative and 10 miRNAs with a positive effect. Testing reciprocal Th17 differentiation revealed specific functions for miR-100, miR-99a and miR-10b, since all of these promoted the Treg and inhibited the Th17 program without impacting on viability, proliferation and activation. miR-99a cooperated with miR-150 to repress the expression of the Th17-promoting factor mTOR. The comparably low expression of miR-99a was strongly increased by the Treg cell inducer "retinoic acid", and the abundantly expressed miR-150 could only repress Mtor in the presence of miR-99a. Our data suggest that induction of Treg cell differentiation is regulated by a miRNA network, which involves cooperation of constitutively expressed as well as inducible miRNAs.

Potentiation of the store-operated calcium entry (SOCE) induces phytohemagglutinin-activated Jurkat T cell apoptosis

Store-operated Ca(2+) entry (SOCE) is the main Ca(2+) entry pathway of non-excitable cells. In the past decade, the activation of this entry has been unveiled, with STIM1, a protein of the endoplasmic reticulum able to sense the intraluminal Ca(2+) content, and Orai1, the pore-forming unit of the Ca(2+) release activated Ca(2+) (CRAC) channels. When Ca(2+) ions are released from the endoplasmic reticulum, STIM1 proteins oligomerize and directly interact with Orai1 proteins, allowing the opening of the CRAC channels and a massive Ca(2+) ion influx known as SOCE. As Ca(2+) is involved in various cellular processes, the discovery of new drugs acting on the SOCE should be of interest to control the cell activity. By testing analogs of 2-aminoethyl diphenylborinate (2-APB), a well known, though not so selective effector of the SOCE, we identified methoxy diethylborinate (MDEB), a molecule able to potentiate the SOCE in three leukocyte and two breast cancer cell lines by increasing the Ca(2+) influx amplitude. Unlike 2-APB, MDEB does not affect the Ca(2+) pumps or the Ca(2+) release from the endoplasmic reticulum. MDEB could therefore represent the first member of a new group of molecules, specifically able to potentiate SOCE. Although not toxic for non-activated Jurkat T cells, it could induce the apoptosis of phytohemagglutinin-stimulated cells.

Placing ion channels into a signaling network of T cells: from maturing thymocytes to healthy T lymphocytes or leukemic T lymphoblasts

T leukemogenesis is a multistep process, where the genetic errors during T cell maturation cause the healthy progenitor to convert into the leukemic precursor that lost its ability to differentiate but possesses high potential for proliferation, self-renewal, and migration. A new misdirecting "leukemogenic" signaling network appears, composed by three types of participants which are encoded by (1) genes implicated in determined stages of T cell development but deregulated by translocations or mutations, (2) genes which normally do not participate in T cell development but are upregulated, and (3) nondifferentially expressed genes which become highly interconnected with genes expressed differentially. It appears that each of three groups may contain genes coding ion channels. In T cells, ion channels are implicated in regulation of cell cycle progression, differentiation, activation, migration, and cell death. In the present review we are going to reveal a relationship between different genetic defects, which drive the T cell neoplasias, with calcium signaling and ion channels. We suggest that changes in regulation of various ion channels in different types of the T leukemias may provide the intracellular ion microenvironment favorable to maintain self-renewal capacity, arrest differentiation, induce proliferation, and enhance motility.

Effects of embryonic cyclosporine exposures on brain development and behavior

Cyclosporine, a calcineurin inhibitor, is successfully used as an immunosuppressant in transplant medicine. However, the use of this pharmaceutical during pregnancy is concerning since calcineurin is thought to play a role in neural development. The risk for human brain development is difficult to evaluate because of a lack of basic information on the sensitive developmental times and the potentially pleiotropic effects on brain development and behavior. In the present study, we use zebrafish as a model system to examine the effects of embryonic cyclosporine exposures. Early embryonic exposures reduced the size of the eyes and brain. Late embryonic exposures did not affect the size of the eyes or brain, but did lead to substantial behavioral defects at the larval stages. The cyclosporine-exposed larvae displayed a reduced avoidance response to visual stimuli, low swim speeds, increased resting, an increase in thigmotaxis, and changes in the average distance between larvae. Similar results were obtained with the calcineurin inhibitor FK506, suggesting that most, but not all, effects on brain development and behavior are mediated by calcineurin inhibition. Overall, the results show that cyclosporine can induce either structural or functional brain defects, depending on the exposure window. The observed functional brain defects highlight the importance of quantitative behavioral assays when evaluating the risk of developmental exposures.

New Compound Classes: Protein-Protein Interactions

"Protein-protein interactions (PPIs) are one of the most promising new targets in drug discovery. With estimates between 300,000 and 650,000 in human physiology, targeted modulation of PPIs would tremendously extend the "druggable" genome. In fact, in every disease a wealth of potentially addressable PPIs can be found making pharmacological intervention based on PPI modulators in principle a generally applicable technology. An impressing number of success stories in small-molecule PPI inhibition and natural-product PPI stabilization increasingly encourage academia and industry to invest in PPI modulation. In this chapter examples of both inhibition as well as stabilization of PPIs are reviewed including some of the technologies which has been used for their identification."

Duality of the murine CD8 compartment

CD8αβ plays crucial roles in the thymic selection, differentiation, and activation of some, but not all, CD8(+) T cells, whereas CD8αα does not. To investigate these roles, we produced mice that expressed transgene P14 T-cell receptor β (TCRβ) chain and CD8β or did not (WT and KO mice, respectively). The primary CD8(+) T-cell response to acute lymphocytic choriomeningitis virus (LCMV) infection was predominantly D(b)/GP33 specific and CD8 independent in KO mice and was mostly CD8 dependent in WT mice. Cytotoxic T lymphocytes (CTL) from KO mice failed to mobilize intracellular Ca(2+) and to kill via perforin/granzyme. Their strong Fas/FasL-mediated cytotoxicity and IFN-γ response were signaled via a Ca(2+)-independent, PI3K-dependent pathway. This was also true for 15-20% of CD8-independent CTL found in WT mice. Conversely, the perforin/granzyme-mediated killing and IFN-γ response of CD8-dependent CTL were signaled via a Ca(2+), p56(lck), and nuclear factor of activated T cells-dependent pathway. Deep sequencing of millions of TCRα chain transcripts revealed that the TCR repertoires of preimmune CD8(+) T cells were highly diverse, but those of LCMV D(b)/GP33-specific CTL, especially from KO mice, were narrow. The immune repertoires exhibited biased use of Vα segments that encoded different complementary-determining region 1α (CDR1α) and CDR2α sequences. We suggest that TCR from WT CD8-independent T cells may engage MHC-peptide complexes in a manner unfavorable for efficient CD8 engagement and Ca(2+) signaling but permissive for Ca(2+)-independent, PI3K-dependent signaling. This duality of the CD8 compartment may provide organisms with broader protective immunity.

Calcineurin interacts with the serotonin transporter C-terminus to modulate its plasma membrane expression and serotonin uptake

Homeostasis of serotonergic transmission critically depends on the rate of serotonin reuptake via its plasma membrane transporter (SERT). SERT activity is tightly regulated by multiple mechanisms, including physical association with intracellular proteins and post-translational modifications, such as phosphorylation, but these mechanisms remain partially understood. Here, we show that SERT C-terminal domain recruits both the catalytic and regulatory subunits of the Ca(2+)-activated protein phosphatase calcineurin (CaN) and that the physical association of SERT with CaN is promoted by CaN activity. Coexpression of constitutively active CaN with SERT increases SERT cell surface expression and 5-HT uptake in HEK-293 cells. It also prevents the reduction of 5-HT uptake induced by an acute treatment of cells with the protein kinase C activator β-PMA and concomitantly decreases PMA-elicited SERT phosphorylation. In addition, constitutive activation of CaN in vivo favors 5-HT uptake in the adult mouse brain, whereas CaN inhibition reduces cerebral 5-HT uptake. Constitutive activation of CaN also decreases immobility in the forced swim test, indicative of an antidepressant-like effect of CaN. These results identify CaN as an important regulator of SERT activity in the adult brain and provide a novel molecular substrate of clinical interest for the understanding of increased risk of mood disorders in transplanted patients treated with immunosuppressive CaN inhibitors.

Structural characterization of the interaction of human lactoferrin with calmodulin

Lactoferrin (Lf) is an 80 kDa, iron (Fe³⁺)-binding immunoregulatory glycoprotein secreted into most exocrine fluids, found in high concentrations in colostrum and milk, and released from neutrophil secondary granules at sites of infection and inflammation. In a number of cell types, Lf is internalized through receptor-mediated endocytosis and targeted to the nucleus where it has been demonstrated to act as a transcriptional trans-activator. Here we characterize human Lf’s interaction with calmodulin (CaM), a ubiquitous, 17 kDa regulatory calcium (Ca²⁺)-binding protein localized in the cytoplasm and nucleus of activated cells. Due to the size of this intermolecular complex (∼100 kDa), TROSY-based NMR techniques were employed to structurally characterize Ca²⁺-CaM when bound to intact apo-Lf. Both CaM’s backbone amides and the ε-methyl group of key methionine residues were used as probes in chemical shift perturbation and cross-saturation experiments to define the binding interface of apo-Lf on Ca²⁺-CaM. Unlike the collapsed conformation through which Ca²⁺-CaM binds the CaM-binding domains of its classical targets, Ca²⁺-CaM assumes an extended structure when bound to apo-Lf. Apo-Lf appears to interact predominantly with the C-terminal lobe of Ca²⁺-CaM, enabling the N-terminal lobe to potentially bind another target. Our use of intact apo-Lf has made possible the identification of a secondary interaction interface, removed from CaM’s primary binding domain. Secondary interfaces play a key role in the target’s response to CaM binding, highlighting the importance of studying intact complexes. This solution-based approach can be applied to study other regulatory calcium-binding EF-hand proteins in intact intermolecular complexes.

Cyclophilin inhibitors: an emerging class of therapeutics for the treatment of chronic hepatitis C infection

The advent of the replicon system together with advances in cell culture have contributed significantly to our understanding of the function of virally-encoded structural and nonstructural proteins in the replication cycle of the hepatitis C virus. In addition, in vitro systems have been used to identify several host proteins whose expression is critical for supporting such diverse activities as viral entry, RNA replication, particle assembly, and the release of infectious virions. Among all known host proteins that participate in the HCV replication cycle, cyclophilins are unique because they constitute the only host target that has formed the basis of pharmaceutical drug discovery and drug development programs. The introduction of the nonimmunosuppressive cyclophilin inhibitors into clinical testing has confirmed the clinical utility of CsA-based inhibitors for the treatment of individuals with chronic hepatitis C infection and has yielded new insights into their mechanism(s) of action. This review describes the biochemical evidence for the potential roles played by cyclophilins in supporting HCV RNA replication and summarizes clinical trial results obtained with the first generation of nonimmunosuppressive cyclophilin inhibitors.

Calcium/calmodulin-dependent protein kinase II regulates IL-10 production by human T lymphocytes: a distinct target in the calcium dependent pathway

Calcium (Ca2+) plays an essential role in lymphocyte activation and differentiation by affecting signaling pathways leading to cytokine production. Among the enzymes responding to calcium increase, Ca2+/calmodulin-dependent protein kinase II (CaMKII) has been involved in anergy with a still poorly characterized role. IL-10 produced by different T lymphocyte subpopulations is critical mediator of tolerance. We tested the hypothesis that CaMKII may be involved in IL-10 production. We report that CaMKII upregulates IL-10 production by primary human T lymphocytes stimulated through the antigen receptor or bypassing that. Overexpression of constitutively active mutant forms of Calcineurin or CaMKII specifically increase IL-10 protein product and IL-10 mRNA accumulation in T lymphocytes. By cotransfecting constitutively active CaMKII with luciferase reporter plasmids carrying specific fragments or the whole IL-10 promoter, we show that CaMKII specifically activates IL-10 promoter activity, whereas it inhibits IL-2 and IL-4 promoter. This effect is mediated by the first 500 bp fragment, which contains binding sites for Myocyte Enhancer Factor-2 (MEF2). A constitutively active mutant of CaMKII activated a luciferase reporter plasmid under the control of MEF2, when cotransfected in T lymphocytes stimulated by Ionomycin and PMA, whereas its inhibitor KN-62 inhibited MEF2 binding in cell lysates of the same cells. Moreover, overexpression of MEF2 enhanced by 2.5-fold IL-10 promoter activity. Our data for the first time suggest a distinct role of CaMKII in the induction of anergy in T lymphocytes, by differential regulation of IL-10 and IL-2 gene transcription suggest MEF2 as a molecular target which can integrate different calcium signals.

Endoplasmic reticulum calcium pumps and cancer cell differentiation

The endoplasmic reticulum (ER) is a major intracellular calcium storage pool and a multifunctional organelle that accomplishes several calcium-dependent functions involved in many homeostatic and signaling mechanisms. Calcium is accumulated in the ER by Sarco/Endoplasmic Reticulum Calcium ATPase (SERCA)-type calcium pumps. SERCA activity can determine ER calcium content available for intra-ER functions and for calcium release into the cytosol, and can shape the spatiotemporal characteristics of calcium signals. SERCA function therefore constitutes an important nodal point in the regulation of cellular calcium homeostasis and signaling, and can exert important effects on cell growth, differentiation and survival. In several cell types such as cells of hematopoietic origin, mammary, gastric and colonic epithelium, SERCA2 and SERCA3-type calcium pumps are simultaneously expressed, and SERCA3 expression levels undergo significant changes during cell differentiation, activation or immortalization. In addition, SERCA3 expression is decreased or lost in several tumor types when compared to the corresponding normal tissue. These observations indicate that ER calcium homeostasis is remodeled during cell differentiation, and may present defects due to decreased SERCA3 expression in tumors. Modulation of the state of differentiation of the ER reflected by SERCA3 expression constitutes an interesting new aspect of cell differentiation and tumor biology.

CBP501-calmodulin binding contributes to sensitizing tumor cells to cisplatin and bleomycin

CBP501 is an anticancer drug currently in randomized phase II clinical trials for patients with non-small cell lung cancer and malignant pleural mesothelioma. CBP501 was originally described as a unique G(2) checkpoint-directed agent that binds to 14-3-3, inhibiting the actions of Chk1, Chk2, mitogen-activated protein kinase-activated protein kinase 2, and C-Tak1. However, unlike a G(2) checkpoint inhibitor, CBP501 clearly enhances the accumulation of tumor cells at G(2)-M phase that is induced by cisplatin or bleomycin at low doses and short exposure. By contrast, CBP501 does not similarly affect the accumulation of tumor cells at G(2)-M that is induced by radiation, doxorubicin, or 5-fluorouracil treatment. Our recent findings point to an additional mechanism of action for CBP501. The enhanced accumulation of tumor cells at G(2)-M upon combined treatment with cisplatin and CBP501 results from an increase in intracellular platinum concentrations, which leads to increased binding of platinum to DNA. The observed CBP501-enhanced platinum accumulation is negated in the presence of excess Ca(2+). Some calmodulin inhibitors behave similarly to, although less potently than, CBP501. Furthermore, analysis by surface plasmon resonance reveals a direct, high-affinity molecular interaction between CBP501 and CaM (K(d) = 4.62 × 10(-8) mol/L) that is reversed by Ca(2+), whereas the K(d) for the complex between CBP501 and 14-3-3 is approximately 10-fold weaker and is Ca(2+) independent. We conclude that CaM inhibition contributes to CBP501's activity in sensitizing cancer cells to cisplatin or bleomycin. This article presents an additional mechanism of action which might explain the clinical activity of the CBP501-cisplatin combination.